Tongue Salivary Glands Esophagus

• The tongue is a muscular structure enclosed in a mucosal layer of stratified squamous epithelium, well-supplied with blood vessels and richly innervated.
• Lingual tonsils are found in the posterior 1/3 of the tongue
• The dorsal surface of the tongue contains numerous mucosal projections called lingual papillae, which are blood vessels, connective tissue, and epithelium.
• The Mucosa layer of the esophageal wall is composed of stratified squamous epithelium, Lamina propria, and muscularis mucosa.
• The Submucosa layer of the esophageal wall contains esophageal glands and Meissner’s plexus.
• The general structure of the GI tract consists of four layers: Mucosa, submucosa, muscularis, and adventitia/serosa.
• The Adventitia/serosa layer of the esophageal wall is the outermost layer.
• The Muscularis externa layer of the esophageal wall is divided into three parts: Upper, Middle, and Lower part.
• The esophageal wall is composed of several histologic layers: Mucosa, submucosa, muscularis, and adventitia/serosa.
• The muscles of the tongue are both extrinsic and intrinsic, with the fibers oriented in all directions, allowing a high level of mobility.
• Connective tissue between the small fascicles of muscle is penetrated by the lamina propria, making the mucous membrane strongly adherent to the muscular core.
• The tongue has four types of lingual papillae: filiform, fungiform, circumvallate, and foliate.
• Filiform papillae are conical, elongated projections pointing backward, the smallest and most numerous, and the tip is keratinized and lacks taste buds
• Fungiform papillae are mushroom-shaped and located on the margin of the tongue, appearing as red nodules due to thin epithelium contain taste buds on dorsal surface
• Foliate papillae are not abundant in humans, with parallel low ridges separated by deep mucosal clefts, located on the lateral edge of the tongue, and contain taste buds.
• Circumvallate papillae are located on the lateral edge of the tongue, arranged (has taste buds) in a V-shape, dome-shaped, with 8-12 papillae, large, 1-2 mm in diameter, and surrounded by invagination - Ebners glands
• Ebner's glands, associated with the circumvallate

  papillae, drain into the invagination.
• The cells of mucous tubules have flattened, basal nuclei with condensed chromatin.
• The Submandibular Gland primarily secretes through serous acini , with many mixed mucous acini (demilunes), secreting α-amylase and proline-rich proteins, and also secretes lysozyme for hydrolysis of bacterial walls - Striated ducts together with intercalated ducts can be seen
• Serous acini contain serous cells and are generally spherical.
• Mucous Acini are usually more tubular than serous acini.
• Intercalated ducts in the Salivary Duct System are lined by low cuboidal epithelium and are the longest in the parotid gland, secreting HCO3- and absorbing Cl-.
• Mucus is synthesized and stored within the cell apex as mucinogen granules.
• The outer surface of the acinus is surrounded by contractile myoepithelial cells in a basket-like fashion.
• In the proximal portion of the duct system, myoepithelial cells are involved in moving secretory products.
• In H&E preparations, mucous acini have a cap of serous cells called serous demilunes.
• Serous cells in the Parotid Gland secrete abundant α-amylase that initiates hydrolysis of carbohydrates and proline-rich proteins with antimicrobial and other protective properties

  Adipose tissue can be seen along with long intercalated ducts and large straited ducts
• Striated ducts in the Salivary Duct System are lined by cuboidal to columnar epithelium and have many infoldings of their basolateral membrane aligned with mitochondria, reabsorbing Na+ and secreting K+ and HCO3-.
• Myoepithelial cells and the acinus are enclosed by a basal lamina.
• Mixed acini contain both serous and mucous cells.
• Mucous acini contain mucous cells and are usually more tubular.
• The nucleus of an acinus is typically flattened against the base of the cell.
• Excretory ducts in the Salivary Duct System include interlobular ducts, lined by pseudostratified columnar epithelium, and interlobar ducts, lined by stratified columnar epithelium.
• The Sublingual Glands secrete a mixed serous and mucous secretion, with mucous cells predominating, the main product of which is mucus - The intercalated and striated ducts are poorly developed
• Salivary Duct System (overview) includes intralobular, interlobar, and interlobular ducts.
• Numerous taste buds are present on the lateral surface of the foliate papillae.
• The lamina propria of the esophagus is a loose fibroelastic connective tissue, containing diffuse lymphatic tissue and cardiac glands in the terminal part of the esophagus.
• The muscularis externa of the esophagus consists of an inner circular layer and an outer longitudinal layer, the upper 1/3 striated, the middle 1/3 mixed, and the lower 1/3 smooth.
• The submucosa of the esophagus is dense irregular connective tissue, containing larger blood and lymphatic vessels, nerve fibers, and ganglion cells that make up the submucosal plexus (Meissner’s plexus).
• The muscularis mucosae of the esophagus is composed of longitudinally organized smooth muscle, helping with swallowing.